Electrical filter system



Feb. 13, 1934. B. F. MIESSNER ELECTRICAL FILTER SYSTEM Filed May 3, 1929351 Gum/nu 60 grid of tube 8 Patented Feb. 13, 1%34 more STATE 1,947,218ELECTRICAL FILTER SYSTEM Benjamin F. Miessner, S

y of America, Delaware hort Hills, N. J assignor, mesne assignments, toRadio Corporation New York, N. Y., a corporation of Application May 3,1929. Serial No. 360,042

17 Claims.

My present invention relates generally to electrical filter systems, andmore particularly to a system for filtering or smoothing out thefiuctuations or ripples in a fiuctuating source of uni- 5 directionalelectrical current supply before delivery to a work circuit or loadrequiring substantially steady energizing.

One object of my invention is the energizing of the output and inputelectrodes of three elec trode vacuum tubes in amplifying systems withrectified alternating current from the usual co1nmercially availablealternating current sources with little or no resulting hum.

A feature of my invention is the employment 'of the characteristics of athree electrode vacuum tube or its equivalent as an aid in the filteroper ation either independently or in conjunction with its functioningin another usual manner.

The novel features which I believe to be characteristic of my inventionare set forth in particularity in the appended claims, the inventionitself, however, as to both its organization and method of operationwill best be understood by reference to the following description takenin connection with the drawing in which I have indicateddiagrammatically several circuit organizations whereby my invention maybe carried into effect.

The features of my invention will be well under siood by reference tothe figures of the accompanying drawing during the following descriptionthereof, like reference numerals indicating like parts so far aspossible in the two figures.

Fig. l diagrammatically illustrates a filter system embodying featuresof my invention.

Fig. 2 is a modification of the system of Fig. 1 to include a threeelectrode tube in the dual capacity of filter aiding and amplifyingsignal current.

In Fig. 1 the full-wave rectifier 6 rectifies alternatiug current fromsource A. C. with the aid of transformer l and the primary and secondaryelements thereof shown, the output of the rectifier being preferablyshunted by a storage and filtering condenser '7. The unidirectionalcurrent is intended for use in a work circuit 15, which may be forexample the plate circuit or circuits of one or more vacuum tubes of acascaded amplifier. To smooth out the ripples in the rectified current Iinclude a three electrode vacuum tube 8 or its equivalent, the filamentof which is heated with the aid of secondary winding 5, so that thefilament-to-plate path is in series with the current supply from therectifier output to the load 15.

By causing the rectified current to pass through the choke coil 9 andresistance 11, both shunted by a ripple governing condenser 10, I candevelop such pulsating unidirectional potential on the that the amountof filament-toplate current can be controlled as well as opposing theripple therein to any desired degree by the pulsations thus introducedon and controlled at the grid. The inclusion of inductance andresistivity in coil 9, resistivity in resistance 11, and capacity incondenser 10, allows for developing the desired degree of grid biasingpotential and controlling for the desired amount and phase of thefluctuation potential on the grid to regulate the amount of current flowthrough load 15 and to eliminate the ripple therein.

In the event the impedance through the space current path and load issuch that suificient ripple current cannot be developed on the grid tosmooth out the load current ripple to the desired amount the inclusionof a condenser 12 to provide a lesser impedance for the fluctuatingcomponent can be used to advantage. A condenser 14 may be employed toprevent actions in the load circuits from being reflected back into thefilter system; for example, signal currents, if the load comprises thetubes of a signal current amplifying system.

The system of Fig. 2 differs from that of Fig. 1 in that I employ thetube 8 in the dual capacity of filtering and signal amplifying, as forexample the output tube of a cascade system in which the tube 17 is apreceding amplifier or detector. This I accomplish by introducing thesignal current output of tube 17 into the grid circuit of tube 8 throughtransformer 19, tube 17 having a signal current input throughtransformer or other coupling element 18. The signal current output oftube 8 may be transmitted to a loud speaker or other translating devicethrough transformer 20 and condenser 25.

The plate current of tube 17 forms the load on the filter system, orthere may be a plurality of tubes in cascade or otherwise, the filamento-r filaments being heated with the aid of transformer secondary 16. Theplate current of tube 1'? is shown to pass through resistance 22 toproduce a grid biasing potential for this tube.

In the event the desired grid bias for tube 8 cannot be created by theresistance of coil 9 and shunted resistance 11 in their designs forother purposes, then the inclusion of a resistance 21 will aid inadjusting in the desired manner. Likewise, connection of condenser 12 toan intermediate point 24 of coil 9 may facilitate adjustment for loadcurrent ripple elimination.

In the systems of both Figs. 1 and 2 it is preferable to use a vacuumtube 8 having filament characteristics of the type disclosed in mycopending application scrim No. 191,195, filed 13 May 1927, which issuedon June 18th, 1929 as U. S. Patent No. 1,718,059, or a so-calledindirectly heated type of cathode, this in order to avoid disturbancesarising from energizing the filament or cathode with alternatingcurrent.

No limitations are intended through the confining of my description andexplanation to the specific embodiments of the figures of the drawingother than those imposed by the appended claims.

Having fully described my invention I claim:

1. In an electrical current supply system, the combination of a sourceof fluctuating unidirectional current, a work circuit adapted to beenergized by said source, an electron tube, the filament-plate path ofwhich is series connected between said source and said work circuit, andmeans for varying the impedance of said filament plate path inconsonance with the fiuctuating component of said source, whereby saidfluctuating component of said source is isolated from said work circuit,said means consisting of a parallel connected choke coil, condenser andresistance system connected in series between the I filament of saidtube and one terminal of said source, the grid of said tube beingconnected to the source side of said choke coil, and a variablecondenser connected between the other terminal of said source and saidchoke coil.

2. In an electrical system, the combination of a source of pulsatingdirect current, a work circuit, a filter system connected between saidsource and said work circuit, said filter system including amulti-electrode tube, the cathode-plate path of said tube being seriesconnected be tween said source and said work circuit, and meansincluding a choke coil and an adjustable capacity in shunt with saidcoil, in said series connection, and a direct current connection betweenthe control grid of the tube and a point on said means such that apulsation compensating potential is impressed upon said control gridfrom said filter system whereby the space current of said tube ismaintained sub stantially free from variation due to the variations ofsaid source.

Ii In an electrical system, the combination of a source of pulsatingdirect current, a work circuit, a filter system connected between saidsource and said work circuit, said filter system including a threeelectrode tube, the filament-plate path of said tube being seriesconnected between said source and said work circuit, means forenergizing the grid of said tube from said filter system whereby thespace current of said tube is maintained substantially free fromvariation due to the variations of said source, means for impressingsignal current variations upon the grid of said tube whereby the spacecurrent of said tube is varied in consonance with said signal currentvariations, and means associated with the plate-filament circuit of saidtube for abstracting a portion of the signal component of said spacecurrent for the production of audible signals.

4. In an electrical system, the combination of a source of pulsatingunidirectional current, a work circuit deriving energy from said source,a choke coil and condenser filter system connected between said sourceand said work circuit, said filter system inluding a three electrodetube, the filament-plate path of said tube being series related to saidchoke coil and between said condensers, a variable capacitor in shuntwith the coil, and means for energizing said grid from said choke coilwhereby the space current of said tube is substantially free fromvariations in intensity due to the variations of said source.

5. In an electrical system, the combination of a source of pulsatingunidirectional current, a Work circuit deriving energy from said source,a

choke coil and condenser filter system connected between said source andsaid work circuit, said filter system including a three electrode tube,the filament-plate path of said tube being series related to said chokecoil and between said condensers, means for energizing said grid fromsaid choke coil whereby the space current of said tube is substantiallyfree from variations in intensity due to the variations of said source,means for impressing signal current variations upon the grid of saidtube whereby the space current of said tube is varied in consonance withsaid signal, and means associated with the plate-filament circuit ofsaid tube for abstracting at least a portion of the signal component ofsaid space current for the production of audible signals.

6. In an electrical system, the combination of a source of pulsatingunidirectional current, a work circuit, including at least one amplifiertube deriving energy from said source, a choke coil and condenser filtersystem connected between said source and said work circuit, said filtersystem including a three electrode tube, the filament-plate path of saidtube being series related to said choke coil and between saidcondensers, means for energizing said grid from said filter systemwhereby the space current of said three electrode tube is substantiallyfree of variations in intensity due to said source, means for impressingsignal currents upon the input circuit of said amplifier tube, meanscoupling the output circuit of said amplifier tube to the gridfiiamentcircuit of said three-electrode vacuiun tube, and means associated withthe plate-filanient circuit of said three electrode tube whereby thesignal component of the space current of said tube is made audible.

7. In an electrical system including a source of pulsatingunidirectional current, a work circuit and a filter system connectedbetween said source and said work circuit, said filter system consistingof the combination of a filter condenser connected across the terminalsof said source, a direct connection between one terminal of said sourceand one terminal of said work circuit, a filter choke coil and a threeelectrode tube, said choke coil and the filament-plate path of said tubebeing series related between the other terminal of said source and theother terminal of said work circuit, a condenser connected across theterminals of said work circuit, an adjustable capacitative reactance inshunt with the coil and means for energizing the grid of said tube fromsaid source whereby the potential across the terminals of said workcircuit is substantially free of any fluctuating component of saidsource.

8. In an electrical system including a. source til of pulsatingunidirectional current, a work circuit and a filter system of said workcircuit, a condenser connected across v the terminals of said workcircuit, and means for energizing the grid of said tube from said sourcewhereby the potential across the terminals of said work circuit issubstantially free of any fluctuating component of said source, said Ameans consisting of a condenser connected beconnected between saidsource and said work circuit, said filter system the terminals of said.

tween a point in said choke removed from the source connection thereofand the other terminal of said source, and a condenser in shunt to saidchoke.

9. In electrical system including a source of pulsating unidirectionalcurrent, a work circuit and a filter system connected between saidsource and said work circuit, said filter system consisting of thecombination of a filter condenser connected across the terminals of saidsource, a direct connection between one terminal of said source and oneterminal of said work circuit, a filter choke coil and a three electrodetube, said choke coil and the filament-plate path or" said tube beingseries related between the other terminal of source and the otherterminal of said work circuit, a condenser connected across theterminals of said work circuit, and means for energizing the grid ofsaid tube from said source whereby the potential across the terminals ofsaid work circuit is substantially free of any fluctuating component ofsaid source, said means consisting of a condenser connected between apoint in said choke removed from the source connection thereof and theother terminal of said source, and a condenser and resistance parallelconnected in shunt to said choke.

10. In an electrical system the combination of a source of pulsatinguni-directional current, an amplifier circuit, a filter system includinga multi-electrode tube connected therein so that the amplifier currentflows in the cathode to anode path of the tube to said amplifiercircuit, means through which said pulsating current flows connected tothe grid of said tube for introducing thereon a pulsating potentialacting to neutralize in said tube pulsations in the amplifier currentpassing therethrough, and additional means for coupling the output ofsaid amplifier circuit to the input of said tube.

11. In an electrical system the combination of a source of pulsatinguni-directional current, a signal amplifier circuit, a filter systemincluding a multi-electrode tube connected therein with its cathode toanode path in series with said amplifier circuit, conections fordeveloping from said pulsating current controlling pulsating currentpotentials on the grid of said tube for establishing a non-pulsatingcurrent of desired magnitude thereon, signal input and output meansassociated with said tube, and means for connecting the amplifier outputto the signal input of said tube.

12. In an electric current supply system, the combination or" a sourceof fluctuating unidirectional current, a single amplifier circuitadapted to be energized by said source, a second amplifier seriesconnected between said source and said first amplifier circuit, meansfor varying the average value of the impedance of said second amplifierand automatically varying said value in consonance with the fluctuatingcomponent of said source, and means for coupling the output or" thefirst amplifier to the input or" the second amplifier.

13. In an electrical current supply system, the combination of a sourceof fluctuating unidirectional current, an amplifier circuit adapted tobe energized by said source, an electron amplifier tube, the cathode toanode path of which is series connected between said source and saidamplifier circuit, means for varying the average value of the impedanceof said cathode to anode path for automatically varying said value inconsonance with the fluctuating component of said source, and means forimpressing the output oi said circuit upon the input of said amplifiertube.

14. In combination, a source of uni-directional pulsating current, anelectron discharge tube provided with signal input and output circuits,a filter system, including an amplifier tube having its input circuitcoupled to said signal output circuit, through which said current flowsto said first tube, and means responsive to current pulsations formaintaining said current flow to the first tube free of pulsations.

15. In combination with a source of pulsating direct current, a loadcircuit, a filter network connecting said load circuit to oppositeterminals of said source, the network including at least one capacitorshunted across said source, a tube having its cathode to anode path inseries between one side of the load circuit and the negative terminal ofthe source, a biasing circuit for the grid of said tube connectedbetween the cathode and grid thereof and comprising a choke coilconnected between said negative terminal and the said cathode, acapacitor in shunt with the coil, and a resistor in shunt with thecapacitor, and an additional capacitor connected between the positiveterminal of said source and a point on said grid biasing circuit.

16. In combination with a source of pulsating direct current, a loadcircuit, a filter network connecting said load circuit to oppositeterminals of said source, the network including at least one capacitorshunted across said source, a tube having its cathode to anode path inseries between one side of the load circuit and the negative terminal ofthe source, a biasing circuit for the grid of said tube connectedbetween the oathode and grid thereof and comprising a choke coilconnected between said negative terminal "and the said cathode, acapacitor in shunt with the coil, and a resistor in shunt with thecapacitor, and an adjustable capacitor connected between the positiveterminal of said source and a point on the coil of said grid biasingcircuit and a variable resistor in series with the coil.

17. In combination with a source of pulsating direct current, a loadcircuit, a filter network connecting said load circuit to oppositeterminals of said source, the network including at least one capacitorshunted across said source, a tube having its cathode to anode path inseries between one side of the load circuit and the negaive terminal ofthe source, a biasing circuit for the grid of said tube connectedbetween the oathode and grid thereof and comprising a choke coilconnected between said negative terminal and the said cathode, acapacitor in shunt with the coil, a resistor in shunt with thecapacitor, and an additional capacitor connected between the positiveterminal of said source and a point on said grid biasing circuit, saidload circuit comprising an amplifier tube having its anode ccnductivelyconnected to the positive terminal of the source and inductively coupledto the grid circuit of said first tube, a direct current connectionincluding a grid bias resistor between the anode of the first tube andthe cathode of the amplifier tube, a signal input circuit coupled to thegrid of the amplifier tube and the said last resistor, and a signaloutput circuit coupled to the anode circuit of said first tube.

BENJAMIN F. MIESSNER.

